1. Field of the Invention
The present invention relates to a process for fabricating a semiconductor wafer by surface-grinding both sides of the sliced wafer and then both-side polishing the wafer.
2. Description of the Prior Art
Conventionally, the semiconductor wafer fabricated by surface-grinding both sides of the sliced wafer and then both-side polishing and mirror processing is fabricated by the following steps (shown in FIG. 3)
(1) A silicon single crystal ingot is sliced by an inner diameter saw to obtain a wafer. PA0 (2) The peripheral portion of the sliced wafer is chamfered to prevent the generation of indentation on the peripheral portion. PA0 (3) The both sides of the chamfered wafer is surface-ground to form uniform thickness. PA0 (4) The surface-ground wafer is washed with water to remove contaminants. PA0 (5) The both sides of the washed wafer are polished simultaneously and mirror processed by a both-side polishing machine. At that time, the wafer to be polished is kept clamped in the template. In order to prevent the wafer from being contaminated by metal, the template is preferably made of resin. PA0 (6) After the mirror processing, the wafer is cleaned to remove the impurities including heavy metal and particles and then dried.
However, according to the above-mentioned conventional process, after surface-grinding, a protruded and indented surface, that is, grinding traces 2, is formed on the grinding side of the wafer 3, as shown in FIG. 4. When the wafer 3 is being both-side polished by the both-side polishing machine, the sharp protruded part 2a of the grinding traces 2 is seized by the receiving surface of the polishing cloth 4. Thus, the frictional resistance of the upper and lower tables 5, 6 when rotation of the upper and lower tables is increased. Consequently, the burden on the contact portion 7a of the template contacting the outer portion of the wafer 3 and the burden of the peripheral gears (not shown) of the template 7 increase, resulting in a shortening of the life of the resin template 7.
Further, when the generated frictional resistance is extremely high, the wafer 3 may release from the template 7 and break.
Still further, the polishing cloth 4 may be damaged by the protruded part 2a, thus accelerating the abrading of the polishing cloth 4 and shortening its life.